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‘Blessed tree’ extracts linked to DNA damage

By Andy Coghlan

For some it is a miracle tree, a source of many different medicines. But extracts from the Indian neem tree have now been shown to damage the DNA of sperm when fed to mice.

The researchers who made the discovery think that neem could be a “long-term genetic hazard”, and have called for further investigation to ensure that eating neem products does not produce genetic abnormalities in adults or their children.

Proponents of traditional Hindu Ayurvedic medicine passionately dispute the relevance of the results. “Neem has been used by millions of people in India over several centuries, and there has been no genotoxic effect reported so far,” says Pramila Thakkar of the Neem Foundation, a Mumbai-based charity that promotes products from the neem tree (Azadirachta indica).

But the researchers are standing by their findings. “Application of neem should be restricted, at least,” says Parimal Khan of the Patna Women’s College. He and Kripa Awasthy of the KKM College in Pakur made an extract of neem leaves and fed it daily to male mice for a week.

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A month later, the pair examined sperm-producing cells and sperm from the mice. They will report in a future issue of Food and Chemical Toxicology that as the dose of neem was raised in steps from 0.5 grams to 2.0 grams, the percentage of sperm-producing cells with chromosomal damage rose in tandem, from 18 to 25 per cent. In animals not given neem, the figure was just 5 per cent.

Contraceptive effect

Likewise, they found steadily rising rates of damage to sperm, with 5 per cent of sperm damaged at the lowest dose, rising to 8 per cent at the highest. In controls, fewer than 5 per cent of the sperm were damaged. Sperm counts dropped, too, halving to 6 million per millilitre in mice on the highest doses. Again, the higher the dose, the worse the effect.

It is known that neem blocks sperm, as it is used in contraceptive suppositories. But the fact that it damages sperm cells even when eaten is worrying. Neem is still widely used in India, and a large range of neem products is now available in health food stores in western countries.

Khan says that the results echo their findings in 1999 that mice given neem had an abnormally high incidence of chromosomal abnormalities in their bone marrow cells. He tentatively blames the effect on a constituent of neem called azadirachtin. However, critics dismiss the findings as irrelevant. “It is impossible to determine from this study how the dose of extract compares to the crude weight of neem leaves, the form in which it is usually consumed,” says Vishal Gulati, chairman of the International Ayurveda Foundation in London. He adds that the study only examined the effects of neem substances that dissolve in ethanol, not those soluble in water.

But there have been warnings about neem before, says Alan Cork of the Natural Resources Institute in Greenwich, UK. “We clearly have a lot to learn from this ‘blessed tree’, and not all of it is good news,” he says. “No one should be under the illusion that just because neem products are natural they are safe.”